Technical University of Denmark (DTU) (2012)

Integrated ecohydrological modeling at the catchment scale

Loinaz, Maria Christina

Titre : Integrated ecohydrological modeling at the catchment scale.

Auteur : Loinaz, Maria Christina

Université de soutenance : Technical University of Denmark (DTU)

Grade : Doctoral Thesis (PhD) 2012

Résumé partiel Water resources managers increasingly face the challenge of balancing water
allocation in environments of water scarcity, high food production demand, and
rising pollution levels. Scientists face the challenge of providing managers with
accurate predictions on the outcome of management alternatives that help to
guide the decision process. The need to take a holistic approach and evaluate
interrelated factors that impact the availability of water resources, such as
climate, landscape processes, and surface water interaction with groundwater at
the catchment scale is increasingly recognized. It is through this approach that
human interaction with the environment can be properly assessed. The field of
ecohydrology is an interdisciplinary science that seeks to understand the links
between the physicochemical stressors with biological receptors to support policy
for the sustainability of natural resources.
This PhD study focuses in developing integrated ecohydrological models at the
catchment scale that quantify the changes in receptors caused changes in
environmental stressors as a results of management alternatives. The modeling
approach involves coupling spatially distributed and physically based
hydrological models to process-based ecological models. The output is a measure
of ecological status as a result of a changing environment. The models include
the dynamic interactions between the main components of the hydrologic cycle,
with a focus on surface water and groundwater interactions, which are key
drivers in aquatic ecology. Another key driver in aquatic ecology is stream
temperature, which traditionally has been simulated at the local stream scale with
point source thermal loads. This study has extended the previous work on stream
temperature model development to include diffuse loads at the catchment scale.
The research methodology was applied in two case studies, both located in
agricultural catchments. One case, located in Idaho, US, deals with the issues of
water scarcity, intensive agricultural practices, high stream temperatures, and fish
habitat degradation, which are widespread problems in the Western US. To
evaluate management alternatives for an intensively cultivated valley an
integrated surface water-groundwater and stream temperature model was
developed. The model was coupled to an ecological model that predicts fish
growth as a function of temperature and other factors. Among the main findings
of this study is that groundwater flow has a strong influence on stream
temperature levels and dynamics in areas with high surface water and
groundwater exchange. Moreover, the strong relationship between stream
iv
temperature and the volume and source of streamflow (snowmelt, groundwater,
urban and agricultural runoff) demonstrate the value of temperature data in an
integrated flow model calibration. Land use and water use changes impact both
the surface water and groundwater resources and can thus substantially change
stream temperature dynamics. Local scale factors such as stream vegetation and
geomorphology also play an important role in determining stream temperature.
Thus, a combination of restoration strategies must be evaluated to find the
optimal thermal conditions. Fish optimal growth and sustainability is dependent
on a specific range of temperatures, but is also affected by seasonal variability,
which should be taken into account when evaluating restoration altern